Light emitting diode (LED) based luminaires often comprise LED modules comprising printed circuit boards (PCBs) on which LED elements are mounted with electrical connections to the PCB for supplying power to the LED elements. The LED elements are typically arranged in an array or pattern and mounted on the PCB, often termed PCB assembly (PCBA), which is appropriate for the luminaire in which they are to be used. Whilst each LED element comprises a light source with a primary optical element or lens, secondary optical elements are often required to direct the light produced by these light sources in directions appropriate to the particular implementation in a luminaire. Lenses are typically used as the secondary optical elements for directing the light.
For outdoor use, such LED modules together with their secondary optical elements are mounted within an enclosure having a window made of glass or polycarbonate to ensure that there is proper protection of the LED modules against the ingress of water. The window, whilst allowing light from the LED modules to be transmitted from the enclosure, forms another optical interface which generates additional light losses due to attenuation. Typically, light losses of up to around 7% are common for glass windows used for outdoor luminaires.
It is possible to reduce these light losses by using the material from which the secondary optical elements or lenses are made as the protective window. In such an assembly, the LED module is enclosed between a back surface and a surface formed by an array of secondary optical elements to form a sealed enclosure. Whilst such an arrangement may provide adequate protection for the LED module, it is still essential to provide wires to the LED module and water-tightness around the wires that extend into the sealed enclosure remains a source of water ingress if they are not properly surrounded by a suitable gasket material which maintains the seal for the enclosure.
CN-U-202947010 discloses a solution to this problem by providing a water-tight cable gland or gasket on a back surface of such a sealed enclosure through which wires enter into the sealed enclosure. However, whilst such a solution is suitable for LED modules having their own thermal heat sinks, it complicates the assembly of flat LED modules when they need to be mounted to a flat surface of a luminaire body as grooves and holes need to be provided to allow for the routing of wires and cables to the LED modules.
WO-A-2011/053349 discloses a mounting arrangement a LED module in which a gasket is provided over a rigid secondary lens array and which is held in place by a cover. The cover forms, with a base on which the LED module is mounted, an interior which encloses and compresses the gasket against the secondary lens array and the secondary lens array against the PCBA to form a sealed enclosure when screwed together. The gasket provides a weatherproof seal and a rigid metal wireway is provided for wiring to the LED module. One such rigid metal wireway is described in U.S. Pat. No. 7,566,147. The wireway is tube-shaped and defines a strong internal passageway through which the wires pass and enter into the sealed enclosure. A seal is placed between one end of the rigid metal wireway and a housing in which the sealed enclosure is mounted.
However, WO-A-2011/053349 requires additional components to form a seal for the LED module but not for the wiring, these additional components not only increasing the complexity of the mounting arrangement but also the cost of such an arrangement. In addition, the rigid metal wireway disclosed in U.S. Pat. No. 7,566,147 also increases complexity and cost as wires need to be carefully threaded through the wireway before the arrangement can be mounted to the housing.